OFDM and OFDMA wireless communication systems under IEEE 802.16 use a network of base stations to communicate with wireless devices (i.e., mobile stations) registered for services in the systems based on the orthogonality of frequencies of multiple subcarriers and can be implemented to achieve a number of technical advantages for wideband wireless communications, such as resistance to multipath fading and interference. Each base station (BS) emits and receives radio frequency (RF) signals that convey data to and from the mobile stations (MS).
The RF signals between a BS and MS may be used to convey data, voice or video. For example, Voice over Internet Protocol (VoIP) is one application in which voice may be transmitted from a MS to a BS and over the internet To support a VoIP application, some systems use an Unsolicited Grant Service (UGS) or extended real time polling service (ertPS) to periodically allocate a bandwidth to the VoIP user. Although, as used herein, VoIP communication may also be via a wired connection.
In normal telephone conversations, generally only about 50% of the full duplex bandwidth is used at any given time. This is because one person is generally listening while the other is talking. When you couple this with the fact that there are natural pauses, pauses for breath and between words, the total required bandwidth for a conversation may be reduced an additional 10%. This means that there is between 50-60% of the available bandwidth that is not being used. Silence suppression techniques take advantage of this by detecting when there is a gap of silence during a conversation and suppressing transmissions during the silence. This silence suppression can improve system performance, as fewer packets sharing the media may result in more consistent delivery of the non-silent packets.